Conventionally, a carbon film etc. is used as a hard mask that is used in an etching process for a semiconductor substrate (see, e.g., Japanese Laid-open Patent Publication No. 2000-133710).
Recently, a boron-based film is attracting attention as a new hard mask material.
Among boron-based films, a boron monofilm has a higher selection ratio than that of a conventional hard mask. However, useful information on a technology for removing the formed boron monofilm from a substrate is not obtained.